Chronic inflammation contributes to atherosclerosis and evidence suggests that innate immune defense[unreadable] mechanisms may interact with proinflammatory pathways and lead to the development of arterial plaques.[unreadable] The innate immune system allows cells to distinguish between pathogen and self by utilizing the signals from[unreadable] Toll-like receptors (TLRs). Recent information also directly implicates signaling by the TLR pathway in these[unreadable] processes, establishing a link between atherosclerosis, defense against foreign pathogens, and[unreadable] endogenously generated inflammatory ligands. TLRs are expressed in vascular cells, specifically[unreadable] atherosclerotic plaque and monocytes. Recent major studies also support the concept that acute infections[unreadable] are associated with a transient increase in the risk of vascular thrombotic events. Although platelets are[unreadable] central in acute thrombotic syndromes and accumulating data demonstrate their role in inflammation, TLRs[unreadable] have not been directly implicated in platelet function. In preliminary data utilizing microarray analyses, we[unreadable] found distinct patterns of platelet gene expression, specifically, TLR2 was increased in patients with acute[unreadable] coronary events and increased TLR1 was associated the presence of diabetes. These findings were[unreadable] confirmed by quantitative RT-PCR, flow cytometry, and confocal microscopy. Proteomic analysis[unreadable] demonstrated the presence of TLR2 in platelets and identified specific TLR2-interacting proteins. Most[unreadable] importantly, incubation of platelets with a TLR2 ligand dose-dependently induced platelet activation and[unreadable] aggregation. Thus, the central hypothesis of this proposal is that innate immunity is relevant to the thrombo-inflammatory response and it is mediated by the expression of TLRs on platelets. To investigate this[unreadable] hypothesis, we propose: Specific aim 1. To further characterize platelet TLR1/TLR2 and determine its role in platelet function. Specific aim 2. To identify and characterize downstream TLR2-dependent signaling pathways in platelets.[unreadable] Specific aim 3. To determine the role of platelet TLR2 in the formation of thrombosis in vivo using a murine[unreadable] model of TLR2 deficiency. Specific aim 4. To study how TLR2 mediates the effects of obesity induced inflammation and platelet reactivity in vivo using a murine model of diet induced obesity.[unreadable] In summary, these studies will further define the role of innate immunity in the processes regulating thrombo-inflammation. These studies will specifically explore the contribution of platelet TLR2 to platelet function and[unreadable] thrombosis in the setting of inflammation.